Network Working Group Pradosh Mohapatra
Internet Draft Rex Fernando
Intended Status: Proposed Standard Eric C. Rosen
Expires: June 12, 2012 Cisco Systems, Inc.
James Uttaro
ATT
December 12, 2011
The Accumulated IGP Metric Attribute for BGP
draft-ietf-idr-aigp-07.txt
Abstract
Routing protocols that have been designed to run within a single
administrative domain ("IGPs") generally do so by assigning a metric
to each link, and then choosing as the installed path between two
nodes the path for which the total distance (sum of the metric of
each link along the path) is minimized. BGP, designed to provide
routing over a large number of independent administrative domains
("autonomous systems"), does not make its path selection decisions
through the use of a metric. It is generally recognized that any
attempt to do so would incur significant scalability problems, as
well as inter-administration coordination problems. However, there
are deployments in which a single administration runs several
contiguous BGP networks. In such cases, it can be desirable, within
that single administrative domain, for BGP to select paths based on a
metric, just as an IGP would do. The purpose of this document is to
provide a specification for doing so.
Status of this Memo
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Mohapatra, et al. [Page 1]
Internet Draft draft-ietf-idr-aigp-07.txt December 2011
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Mohapatra, et al. [Page 2]
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Table of Contents
1 Specification of requirements ......................... 3
2 Introduction .......................................... 3
3 AIGP Attribute ........................................ 5
3.1 Applicability Restrictions and Cautions ............... 6
3.2 Restrictions on Sending/Receiving ..................... 6
3.3 Creating and Modifying the AIGP Attribute ............. 7
3.3.1 Originating the AIGP Attribute ........................ 7
3.3.2 Modifications by the Originator ....................... 8
3.3.3 Modifications by a Non-Originator ..................... 8
4 Decision Process ...................................... 10
4.1 When a Route has an AIGP Attribute .................... 10
4.2 When the Route to the Next Hop has an AIGP attribute .. 11
5 Deployment Considerations ............................. 12
6 IANA Considerations ................................... 12
7 Security Considerations ............................... 12
8 Acknowledgments ....................................... 12
9 Authors' Addresses .................................... 13
10 Normative References .................................. 13
11 Informative References ................................ 14